To the Editor.—The commentary by Berger and Papa, in "Photodye Herpes Therapy—Cassandra Confirmed?" (238:133, 1977) adds heat rather than light to a long-standing debate. Herpes simplex viral infections of the genitalia have been directly associated with the occurrence of squamous cell carcinomas in situ of both the vulva and the penis in untreated patients.1,2 A voluminous body of literature similarly implicates the untreated virus with the occurrence of carcinoma of the cervix. Laboratory evidence does indeed suggest that photoinactivated herpes virus is capable of causing cell transformation in tissue cultures. However, there is no evidence to suggest that this therapy is responsible for tumor induction in the adult human. The recent study of Friedrich et al,3 on the contrary, demonstrates that photodynamic dye light therapy has not resulted in the development of epithelial atypia in a series of cases followed by biopsy up to five years after